{"id":"CVE-2026-98985","title":"namespace: check the mounts before reading their parents in pivot_root()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check the mounts before reading their parents in pivot_root()\n\npath_pivot_root() reads the parents of new_root and of the caller's root\nand checks whether th…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < a56d4f8f8f4c5d9ac339d5c03a9d90eecd3697fc","Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 3c2441e21c3df867e4131e0ff784ecdb3a7a55f8","Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < e3aba6900483f64e6c9eb328150dd633b7d36c1c","Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 3dad2330c89343ba083cf7868779083fd5fbe0fe","Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 6b7c001eb5857fa09041f47673666060a2e5fc1c","Linux 84b78514033ff22c443473214ab6d0508394cf7a","Linux >= 4.0.2 < 4.1","Linux 4.1"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:20:03.622Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98985","references":[{"url":"https://git.kernel.org/stable/c/a56d4f8f8f4c5d9ac339d5c03a9d90eecd3697fc"},{"url":"https://git.kernel.org/stable/c/3c2441e21c3df867e4131e0ff784ecdb3a7a55f8"},{"url":"https://git.kernel.org/stable/c/e3aba6900483f64e6c9eb328150dd633b7d36c1c"},{"url":"https://git.kernel.org/stable/c/3dad2330c89343ba083cf7868779083fd5fbe0fe"},{"url":"https://git.kernel.org/stable/c/6b7c001eb5857fa09041f47673666060a2e5fc1c"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.547Z","slug":"CVE-2026-98985","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check the mounts before reading their parents in pivot_root()\n\npath_pivot_root() reads the parents of new_root and of the caller's root\nand checks whether they are shared before it checks that either mount is\nin the caller's mount namespace. Only namespace_sem is held. That's fine\nfor a mount that is in the caller's mount namespace.\n\nBut new_root can be a file descriptor to a mount that has been unmounted\nand that only the file descriptor keeps alive. If that mount stayed\nattached to its parent when it was unmounted nothing pins the parent for\nit. The final mntput() of the parent unhooks the children under\nmount_lock alone and frees the parent afterwards:\n\n  pivot_root()                     close(fd), last ref on the parent\n  ------------                     ---------------------------------\n  ex_parent = new_mnt->mnt_parent\n                                   mntput_no_expire_slowpath()\n                                     __umount_mnt(new_mnt)\n                                   cleanup_mnt()\n                                     call_rcu()\n  IS_MNT_SHARED(ex_parent)\n\n  BUG: KASAN: slab-use-after-free in path_pivot_root+0xf1a/0x1840\n  Read of size 4 at addr ffff8881047382f8 by task pivot_widen/157\n   path_pivot_root+0xf1a/0x1840\n   __x64_sys_pivot_root+0x165/0x190\n\nThe same goes for the caller's root via chroot(). Both outcomes of the\ncheck end in EINVAL so nothing but the read itself goes wrong. It's the\nsame thing commit bb4609405752 (\"statmount: read the parent of an\nunmounted mount under mount_lock\") fixed for statmount().\n\nCheck that both mounts are in the caller's namespace before their\nparents are read. Every path returns EINVAL either way.\n\n## Affected\n\n- `Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < a56d4f8f8f4c5d9ac339d5c03a9d90eecd3697fc`\n- `Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 3c2441e21c3df867e4131e0ff784ecdb3a7a55f8`\n- `Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < e3aba6900483f64e6c9eb328150dd633b7d36c1c`\n- `Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 3dad2330c89343ba083cf7868779083fd5fbe0fe`\n- `Linux >= e0c9c0afd2fc958ffa34b697972721d81df8a56f < 6b7c001eb5857fa09041f47673666060a2e5fc1c`\n- `Linux 84b78514033ff22c443473214ab6d0508394cf7a`\n- `Linux >= 4.0.2 < 4.1`\n- `Linux 4.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}